Electrooptical transmission system



g- 1940' A. GJCOOLEY'EF AL ELECTROQPTICA'L TRANSMISSION SYSTEM.

Filed Mardh 1i, 1939 4Sheet-Shet 1 INVENTOR A. e. COOLEY 51- Al: v ELECTROOPTICAL' TRANSMISSION SYSTEM .1 Sheets-Sheet 2" Filed March 11, 1939 INVENTOR ya- ATTORNEY A g- 1940' A. G. COOLE-Y ET 1. 2,21 ,30

ELECTROOPTICAL TRANSMISSION SYSTEM I Filed March 11, 1939' 4 Sheets-Sheet-6 a IINVENTOR ATTORNEY Aug. 27, 1940.

\ ELEQTROOPTICAL TRANSMISSI ON SYSTEM Filed March 11, 1939 4 Shegts-Shegt 4 A. e. CCOLEY ET AL v 2,212,807

3g MA ZQ v I NVENTOR v C ATTORNEY Patented A ug. 27, 1940 aziasor ELECTROOPTI CAL TRANSMISSION SYSTEM Austin G. Cooley, New York, and Garett Van dcr Veer Dillenback, Jr.,

signers to Wide World Photos, Inc New York, N. Y., a corporation of Ne w'York Slingerlands, N. Y., as-

Application March 11, 1939, Serial No. 261,184

1': Claims. (01. 178 13) This invention relates to electrooptical systems, and more especially to systems for. transmitting'visual representations to a distance and reproducing facsimiles thereof by eiectrooptical means.

A principal object of the invention,relates to a facsimile transmission system having readily adjustable means for varying the speed of trans mission or reproduction.

Another object relates to a system of facsimile I transmission of the type wherein the facsimile signals are in the nature of modulated audio fre-, quency carrier current, and wherein the speed of the scanning equipment at the transmitter or at the receiver can be adjusted while maintaining the .said carrier frequency a constant function of the scanning rate. s

A feature of the invention relates toa gearing arrangement for facsimile scanning drums which is readily changeable to cause'the drum to be rotated at two or more speeds which are harmonies of each other.

Another feature relates to a single specially constructed worm wheel which cooperates with a number. of selectively and interchangeably replaceable worm drives.

Another-featurerelates to a unitary assembly consisting of a readily replaceable worm and stroboscopic indicator.

A further feature relates toa facsimile system employing synchronous driving motors which will operate on the same impressed frequency at two or more harmonically related speeds whereby the speed of transmission or reception can be readily changed.

A further feature relates to a unitary assembly of induction motor and synchronous frequency changer, the induction motor section being wound to operate at either of two speeds from a single frequency source.

A still further feature relates to the method of adjusting an induction motorsynchronous motor combination so as to facilitate attaining and maintaining synchronous speed of the associated scanning equipment. v A still further feature relates to the .novel organization, arrangement and relative location and interconnection of parts whereby a facsimile transmission system can be readily ad- Other features and advantages not specifically enumerated will be apparent from the following detailed description and appended claims. I

Inthe drawings which show certain preferred embodiments of the invention,

Fig. -1 is a schematic composite circuit and apparatus diagram-to illustrate the speed control and'other features of the invention.

Fig. 2 is a top-plan view of part of a driving motor and speed change'unit according to the invention. v

Fig.-3-is a detailed sectional view, of one of the wonn drives and stroboscopic wheel units according to the invention. g s. I

I Fig. 4 is a view of a unit similar to that of Fig. 3, but having a double threaded worm, Fig. 5 is a detailed view of the threaded endof the motor shaft of Fig. '2.

Fig. 6 is a front end elevational view of Fig. 2

with the scanning drum omitted. Fig. 'l is a right-hand elevational view Fig. 6.

Fig. 8 is a detailed view of one of'the bearingmembers.

Fig. 9 isan explanatory diagram showing the manner in which thesingle thread worm 00- operates with the worm wheel of Fig. 2.

Fig.10 is another explanatory diagram to show the manner in which a double thread worm 00- operates with theworm wheel of Fig. 2.

Fig. 11 shows a modification of the invention.

, Fig. 12 is a schematic diagram to explain the method of adjusting the speed of certain parts of the mechanism of Fig. 1.

Fig. 13- is a curve diagrameicplanatory of the 7 operation of Fig. 12.

In the transmission of pictures or other visual displays by electrooptical or facsimile transmission, it very frequently becomes advisable to change rapidly the scanning speed. Thus, in

the case of transmission over telephone lines, the

scanning speed may have to be correlated tothe transmissioncharacteristics of the line. We have found that by using at the transmitter a specially constructed worm wheel for, driving the trans. mitting druin, it is possible to employ readily relplaceableworm drives each having a predetermined thread, for producing the requiredrspeed.

As is well known in facsimile transmissiomthe apparatus must be synchronized with the ut most accuracy and while it may be possible to design a gearing arrangement between the driving motor'and scanning .drum employing ordinary toothed gears, we have found that where the speed is required to'be changed, the requisitespeed is not attainable with ordinary toothed g ceiver.

gear wheels. However, by using a common worm wheel which has the teeth specially hobbed" or formed, it is possible to employ replaceable worms of different numbers of threads and still achievethe desired accuracy. While these interchangeable worms are primarily useful at the transmitter, they may also be used at the re- Referring to Fig. 1, there is shown in schematic form, a facsimile transmission system-embodying the various features of the invention. The transmitting drum l around which the picture or other subject-matter is wrapped. is rotated about its axis, from the motor through the 'worm wheel 2 and the replaceable worm drive 3 which is described in detail in connection with Figs. 2 to 10. A stroboscopic indicator wheel 3 is also carried as a unit by the replaceable worm and is illuminated by the stroboscopic lamp 5 which may be energized by currents from a source whose frequency is known. The members 3 and 4 form a readily replaceable unit with the stroboscope wheel definitely related to the pitch of the worm 3. The line feed for the illuminating optical scanning system 3 is effected by gear wheel 5 and gear wheel 8, the latter being fastened to the lead screw 9 to feed the system 8 which may be of any well known construction.

Associated with the drum is any well known form of light sensitive pick-up and modulating arrangement 0. Preferably, although not necessarily, motor drives an A. C. generator (not shown), for example a generator of 1800 cycle current which is fed to the apparatus I over the conductors I2 whereby the 1800 cycle current is "modulated in the device III in accordance with the intensity of the light reflected from each successive elemental area of the picture on drum 1. A detailed description of such modulating system is given in Patent No. 2,015,742.

The amplified picture currents which are impressed on the transmission channel l3, therefore, have a carrier frequency whichis locked to the speed of drum since the motor which drives drum I also drives the A. C. generator. Consequently, as described in said Patent No. 2,015,742, these currents may be used to control the recording lamp at the receiver as well as to synchronize the receiving apparatus'with the transmitter.

The receiver includes a rotatable drum M which is mounted for rotation about its axis in suitable bearings and is driven by a worm wheel carried by the drum shaft, which worm wheel is driven by a worm l6. Drum N is brought up to speed by a two-speed induction motor |1 having two sets of windings for the respective speeds. A common terminal I8 is provided for both windings and individual terminals i9 and 20 are provided for the other windings, these latter terminals being selectively connectable to the supply line by a switch 2|. Preferably, a variable resistance Hg is connected in circuit with the common terminal and the primary of motor I1, and a variable resistance 28 is connected in circuit with the secondary winding of motor for purposes to be described.

When the switch 2| is in the fullline position the motor I! will rotate, for example at 1800*" R. P. M. which would be equivalent to 45 R. P. M. for the drum. Hi. When the switch 2| is in the dotted position, the motor rotates at 3600 R. P. M. which is equivalent to 90 R. P. M. for'* the drum |4. Induction motor I! is mechanicallyconnected to the rotor 22 of't'rsynchronolls motor which controls the synchronous speed of drum i4.

mitter, as well as power supply variations, are

taken by the synchronous motor 22.

The stator winding-23 of the synchronous motor is supplied with part of the received picture carrier current through a double-pole switch 24 when the latter is in the full-line position shown. It will be understood of course, that the received picture signals are suitably amplified in amplifiers 25, 26 and 21, and preferably the amplifier 26 which feeds the stator 23 is biased as will be described in detail hereinbelow inconnection with Figs. 12 and 13. This bias is related to the resistance 28 in circuit with the wound rotor of induction motor IT as will also be described below so as to operate the motor ll on a predetermined portion of its torque-speed characteristic curve. The motor I! willthen be constrained to run at or near the synchronous speed of the motor 22, the latter acting as a speed control for the induction motor. Consequently as the drum l4 approaches the synchronous speed, the motor I! readily falls into step with the received signal.

The position of recording lamp 29 is controlled by the line feed screw 30 driven through worm wheel 8| and worm 32 from a two-speed induction motor 33 similar to motor I 7. Motor 33 -is provided with a switch 34 so as to connect the generator which supplies the carrier current.

to device l0 delivers an A.-C. of 1800 cycles. Under this assumption therefore, switches 2|, 24 and 34, are in their full line positions whereby motors Hand 33 rotate at 3600 R. P. M. Should it be desired to change the speed of rotation of the drum the double-thread worm and stroboscope assembly 3, 4, is removed by loosening thumb nut35, and is replaced by a single-thread worm as described below in connection with Figs. 2 to 10. At the receiver, the double-thread worm l6 may, if desired, be also replaced by a single-thread worm.

Instead of using 'a replaceable worm IE to drive the receiving drum at different speeds, the stator 23 of the synchronous motor can be supplied with a different frequency current which nevertheless is related to the picture carrier, by moving switch 24 to its dotted line position. In this case, the 1800'cycle picture signal which is received over line l3, energizes the stator winding 33 of an 1800 cycle synchronous motor whose rotor is indicated'by the numeral 31. Rotor 31 motor 22, 23, is designed so that it can operate synchronously at two diiferent speeds. for ex-.

operated to its dotted line position, switch 2| was likewise operated to its dotted line position causing motor l1 to run at half speed, thus driving drum H at 45 R. P. M. in synchronism with the drum l-of the transmitter. The line feed motor 33 however, may, if desired, be left running at 3600 R. P. M. but if desired, it-may be run at half speed by operating switch 34 to the dotted line position.

With the foregoing arrangement, the speed of the transmitting drum I, may be rapidly changed merely by replacing the worm and stroboscope unit 3, 4, bythe proper unit. Of cource, in doing so, it is necessary to maintain the same precision of rotation of drum I regardless of which worm is used. We have found that the necessary precision cannot be achieved by using ordinary toothed gear wheels, but that it is necessary'to ,employ a specially hobbed.worm wheel 2 with the cooperating selectable worms 3. Such 'a worm wheel is shown in detail in connection with Figs. 2 to 10.- s

Referring to Figs. 2 to 10, a description will now be given of the selectable speed mechanism which is shown diagrammatically in Fig. 1 for driving drum i. The motor II is preferably of the induction'type' mounted on a suitable base 50. Attached to the motor frame by screws 5| is a bearing housing 52 containing an adjustable eccentric bearing sleeve 53. Bearing 53 is provided'with an adjusting knob 54 whereby the bearing can be rotated through an arc to facili-' tate replacement of the driving worm assembly to be described. Rotatable in the bearing 53 is a shaft 55 to which is fastened the scanning drum I in any well known manner. Suitablyfastened to shaft 55 is a. specially "hobbed worm wheel 2 and the toothed gear- 1 which may be pressed.

against the hub 2aof the worm wheel 2 by spider 2b and fastening nuts 20.

Motor shaft 56 has a reduced threaded end 51 (Fig. 5) and a. detent pin 58. The replaceable worm 3 (Fig. 3) is formed on a hollow sleeve 58 carrying at its forward end.an integral disc-like.

Member 60 is provided with a pair member 60. v of oppositely disposed radial slots 6| which are covered by a translucent disc 62. The threaded end of member 59 is provided with a notch 63 to engage the detent pin 58. Rotatably mounted on the forward end of member 59 is an internally threaded member 64 provided with a knurled knob 65. The internal thread of member 64 engages the threaded shaft 51 and by turning the knob 65 the member 59 is fastened in place, with the detent 58 engaging the notch 83. Member 54 is held longitudinally in place by the inwardly projecting pins 66 which engage the shouldered end of member 64. Consequently, all

properdriving relation between worm .3 and wheel 2 can be had by loosening screw 61 and turning the eccentrically mounted bearing sleeve 53 by means of knob 54, whereupon screw 51 is again tightened to lock the shaft 55 and worm.

wheel 2 in place. For the purpose of illuminating the stroboscope wheel, a small stroboscope lamp socket 68 is worm wheel 2.

insulatinglymounted on the motor frame by means of a bracket 69, one terminal'of the socket being grounded to the frame by lug 10 and the other terminal being insulated from the motor frame and connected to the supply wire 1|. A suitable stroboscope lamp 12 is screwed into socket 58 and is fastened in place by a set screw 13. The worm of Fig. 3 is of the single thread type, and Fig. 4 shows a. corresponding doublej thread worm and stroboscope assembly. for driving the shaft 55-at doublethe speed.

As pointed out above, in order' that a single worm. wheel 2 may be employed with the single and double threaded worms, it is necessary to hob the teeth of the 'worm wheel in such a manner that-they can cooperate with thesame degree ofaccuracy regardless of whether a. single thread worm or double thread worm is employed.

Figs. 9 and 10 show respectively how the'teeth of theworm wheel 2 cooperate withthe associated worms. In Fig. 9, the worm wheel is shown in engagement with a single thread worm, whereas in Fig. 10, the worm wheel 2 is shown in engagegment with a double thread worm. The worm wheel'2 is first cut and hobbedl for the single worm 3, then it is re-hobbed to cooperate with the double thread worm 3a. After being so cut, it will be noticed that when a singlethread worm is used, the forward faces 3b of the worm threads engage the upper rightportions. 3c of the right-hand tooth of the worm wheel (asviewed' in Fig. 9), whereas the rear face 3:! of each worm a thread engages the-lower right face of thesucceeding tooth. on the worm wheel 2. On the 1 other hand, when the double thread worm is used, the corresponding front face 31) of each of the worm threads, engages the lower right face 3e of the worm wheeltooth (as viewed in Fig. 10)

and'the rear face 3d engages the upper right face therefore, there is substantially negligible play or back-lash regardless of whether a single thread worm or a double thread worm is used with the Consequently, the worm and stroboscope units can. be replaced. interchangeably with the same degree of accuracy as regards the rotational movement of drum I.

Instead of using twoseparate worm assembles, the single and double thread worms may be mounted on acommon member so as to be selectively shiftable into engagement with the worm wheel 2. Such an arrangement is shown in Fig. 11. The single thread worm15 and the double thread worm'16 are formed on 'a sleeve member 11 which is adapted to slide along the hollow sleeve member 18. Member .18 corresponds therefore to member .59 of Figs. 2' and 3, and is provided at its forward 'end witha slot 19 to engagethe detent pin 58 on the motorshaft 58. The, left-hand end of sleeve 18 is provided with an integral stroboscope wheel similar to member 60 of Figs. 3 and 4, and an internally threaded member having a knurled knob 8| similar to the member 84 of Fig. 4 is provided for fastening the sleeve 18 to the motor shaft. The sleeve 11 carries thesingle and doube thread worms, and is fastened'in selected position on sleeve 18 by means of a set screw 82 .or the like All that isnecessary therefore, to-change speed with this arrangement, is to unloosen the screw 82 and slide the proper one of the worms 1'5, 16,

into engagement with the worm wheel 2, whereupon the screw 82 may be fastened to lock the worm in adjusted position.

- run much above this point in speed, because As described above, in connection with Fig. 1, the assembly comprising the induction motor ii and the synchronous motor 22--23, is preferably adjusted so as to operate on a particular portion of the speed-torque characteristic curve of the induction motor. A typical speed-torque characteristic of such a motor is shown in Fig. 13, and preferably, the motor is designed and is provided with adjustable means so as to enable it to run at the proper point. Since the synchronous speed is to be determined by the speed of the received carrier current, the synchronous motor rotor 22 is mechanically connected to the shaft 22a of the A. C. induction motor I i. It is desirable that the synchronous motor 22 should come into synchronism with the received carrier without any unnecessary attention on the part of an attendant, and also in the event that the synchronizing signal should fail for a short time, that the motor I! automatically will fall into 'synchronism when the synchronizing signal is reestablished. For this purpose, the incoming signal received over line [3 is fed into an amplifier 26 which has its control grid 26a biased preferably negatively with respect to the cathode 26b, for example by the negative grid .battery 260, so that in the absence of a synchronizing signal applied to the grid 26a, a steady magnetizing current flows through winding 23. The anode circuit of tube 26 includes the stator winding 23 of the synchronous motor. The induction motor comprises a wire wound secondary Ila and a primary winding ill), the latter being connected to a source of power lid .of fixed frequency or through an adjustable resistor I'ig to a source of power of a controllable frequency. The slip rings l'ie, Hf, connect the secondary winding iia'with the variable resistance 28 to permit adjustment of the torque-speed characteristic of the motor. The resistance 28 is adjusted so that when no signal is applied to the stator winding 23 of the synchronous motor, the induction motor I 5 drives the assembly at slightly above synchronous speed at which time the motor operates at point P of its characteristic curve (Fig, 13). The-induction motor will not tend to relatively large load changes cause relatively small speed changes above this point. When the synchronizing signal is applied to the stator 23, there will be exerted a magnetic drag on the rotor 22 which causes the assembly to slow down gradually. As the speed of the assembly approaches synchronous speed, that is, the synchronous speed of rotor 22, the motor I! readily falls into step with the applied signal, which point is indicated by the letter S (Fig. 13) Preferably, the rotor 22 is coupled to the shaft 220.

by any well known form of spring coupling diagrammatically indicated by the numeral 221;.

While certain specific embodiments have been described herein, it will be understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

What we claim is:

1. A gearing arrangement for coupling a facsimile scanner to its driving motor, said gearing arrangement including a worm wheel fixed to the scanner shaft, and a readily detachable worm carried by the motor shaft, said worm carrying integrally therewith a stroboscopic target.

2. A gearing arrangement for coupling a facsimile scanner to its driving motor and including a worm wheel fixed to the scanner shaft, and a hollowtubular member detachabiy secured to the motor shaft and carrying integrally therewith a worm thread.

3. A gearing arrangement for coupling a facsimile scanning drum to its driving motor comprising a worm wheel fixed to the drum shaft, said worm wheel having its teeth hobbed to mesh with either a single or double thread worm, and a member having worm thread carried by the motor shaft and meshing with said worm wheel.

4. A gearing arrangement according to claim 3, in which the motor shaft is provided with a detent and the said member is of hollow form and fitted over the motor shaft and has means to engage said detent.

5. A gearing arrangement according to claim 3, in which the motor shaft has a threaded portion and said member is tubular and has a threaded portion to engage the threaded portion of the shaft, and means to lock said tubular member and motor shaft for rotation as a unit.

6. A coupling arrangement for coupling a facsimile scanner to its driving motor comprising a hollow tubular member having a worm thread on its outer surface, an internally threaded member rotatably fastened in the end of said tubular member, and a stroboscopic target carried by said tubular member.

7. A gearing arrangement according to claim 3 in which the said worm wheel has its teeth hobbed so that one set of diagonally disposed margins of successive teeth are engaged by a single thread worm, and the opposite set of diagonally disposed margins of said teeth are engaged by a double thread worm.

8. A coupling arrangement for coupling a facsimile scanner to its driving motor comprising a worm wheel fastened to the drum shaft, and a worm assembly having a single worm thread portion and a double worm thread portion and adjustably mounted on the motor shaft, whereby the single or double worm thread can be selectively moved into engagement with said worm wheel to vary the speed of said drum.

9. A coupling arrangement according to claim 8, in which the Worm assembly comprises a hollow tubular member adapted to be removably fastened to the motor shaft and another member is slidably mounted on the first tubular member, said other member having'its outer surface provided with said single and double thread worms.

10. A coupling arrangement according to claim 8, in which the drum shaft is provided with an adjustable eccentric bearing mounting to facilitate meshing of the single or double thread worm with said worm wheel.

11. A telefacsimile system comprising a transmitting scanner, a receiving scanner, means to drive said transmitting scanner, means to generate an audio frequency carrier current modulated in accordance with light and shade values, the frequency of said carrier being determined by the speed of said transmitting scanner, a synchronous motor for driving said receiving scanher, said motor being designed to run synchrosaid converter to drive said synchronous. motor at another synchronous speed.

12. A telefacsimile system according to claim 7 11, in which said frequency converter comprises a synchronous motor-generator driven synchronously by part of the received carrier current.

13. Atelefacsimiie system= compising a transmitting scanner, a receiving scanner including a rotatable drum and a line feed mechanism, a

synchronous. motor for rotating said drum, a

motor driving said line feed mechanism, said synchronous motor being designed to operate synchronously at two speeds which are multiples 01' each other, means to receive an audio irequency synchronizing current, a frequency converter, a switch efiective in one position to apply the received current to operate said converter to derive a synchronizing current which is a multiple of the received current as regards frequency, and means to apply said derived current to said synchronous motor, said switch being eifective in another position to apply said received current without conversion to said synchronous motor.

14. A system according to claim 13, in which the received current and the converted current are locked to the speed of the transmitting scanner.

15. A teleiatsimile 'reproducingsystem comprising a rotatable scanning drum adapted to'be driven at two different speeds in accordance with the detail of reproduction desired, means to drive said drum, comprising a two-speed induction motor and a two-speed synchronous motor, means to drive the induction motor being driven from the local power mains and means to drive the synchronousmotor by a synchronizing current received from a distant facsimile transmitter.

16. A telefacsimile reproducing system comprising a rotatable scanning drum with a line I feed device adapted to be driven at two different speeds in accordance with the detail desired in' ner, a gearing arrangement for operating said scanner at multiple speeds including a doubly hobbed worm wheel and a plurality of selectively engageable worms, means to generate a synchronizing current locked to the speed ofsaid drum,

a receiving scanner, means to operate said receiving scanner comprising a. two-speed'synchronous motor operated by the'received synchronizing currents and a two-speed induction motor scanner.

AUSTIN G. COOLEY. GARETT VAN DER VEER DELENBACK, JR,

'coupled to said synchronous motor and receiving 30 

